It is common in the electrical wiring industry -- such as house or industrial wiring and the like -- to connect a plurality of wires in electrically conductive relation by using a twist on wire connector. Typically, twist on wire connectors comprise a plastic insulating cap and a coil of wire contained therein. The cap acts as a insulating housing around the coil and also provides a means for gripping the connector in order to twist it onto the wires. The coil comes in contact with the plurality of wires being connected and protects the cap from being damaged by the wires. The gripping forces necessary to retain the wires in electrically conductive relation inside the coil are provided by either the coil or the cap. If the forces are provided by the cap, they are transmitted to the wires through the coil.
Most caps for twist on connectors used in the electrical industry today, are made of thermosetting resin or similar material. Such types of material have a low modulus of elasticity and thus are not easily elastically deformable, together with a high resistance to plastic deformation -- desirable characteristics of wire connectors. However, more recently it has become desirable to use thermoplastics, such as nylon, as the material used in the manufacture of connector caps for a variety of reasons, such as cost considerations and colour choice. Thermoplastics, however, are relatively elastic and therefore are easily deformed when tightened onto a pair of wires, generally tending to bulge around the periphery. It is possible to make such caps using an injection moulding process, but a cap configuration not specifically designed to be injection moulded most likely cannot be satisfactorily manufactured in this manner primarily due to cooling considerations.